easyexcel 下载

1，依赖

<!-- 3.1.1及以上可以支持分批下载 -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>easyexcel</artifactId>
    <version>3.1.1</version>
</dependency>

2，编码

通用步骤：

1，构建sheet ：设置sheet名称、格式

2，构建ExcelWriter：构建流，excel类型等

3，通过excelWriter将数据写入sheet

1，全量下载

/**
     * write data to excel
     * @param response : 要写入的流
     * @param data : 数据
     * @throws Exception
     */
private void writeData(HttpServletResponse response, List<List<String>> data, String        filename) throws Exception {
        EasyExcel.write(getOutputStream(filename, response), List.class) // 每行的映射类型
                .excelType(ExcelTypeEnum.XLSX)
                .sheet("sheet1")
                .registerWriteHandler(getSheetStyle())
                .doWrite(data);
}
​
/**
     * 设置响应流格式
     * @param fileName 导出的文件名
     * @param response 响应流
     * @return
     * @throws Exception
     */
private OutputStream getOutputStream(String fileName, HttpServletResponse response)         throws Exception {
        fileName = URLEncoder.encode(fileName, "UTF-8");
        response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
        response.setCharacterEncoding("utf8");
        response.setHeader("Content-Disposition", "attachment;filename=" + fileName + ".xlsx");
        response.addHeader("Access-Control-Expose-Headers", "Content-disposition");
        return response.getOutputStream();
}
​
/**
     * set sheet style
     * @return
     */
private HorizontalCellStyleStrategy getSheetStyle() {
        //表头样式
        WriteCellStyle headWriteCellStyle = new WriteCellStyle();
        //设置表头居中对齐
        headWriteCellStyle.setHorizontalAlignment(HorizontalAlignment.LEFT);
        //内容样式
        WriteCellStyle contentWriteCellStyle = new WriteCellStyle();
        //设置内容靠左对齐
        contentWriteCellStyle.setHorizontalAlignment(HorizontalAlignment.LEFT);
        return new HorizontalCellStyleStrategy(headWriteCellStyle, contentWriteCellStyle);
    }

2，分批下载

 // 1, 构建sheet
WriteSheet writeSheet = EasyExcel.writerSheet("sheet1").registerWriteHandler(getSheetStyle()).build();
// 2, 构建ExcelWriter
try(ExcelWriter excelWriter = EasyExcel.write(getOutputStream(fileName, response), List.class).excelType(ExcelTypeEnum.XLSX).build()) {
            // 写入表头
            excelWriter.write(data, writeSheet);
            // 批次
            int batchNum = count / InnerConst.BATCH_SIZE;
            batchNum += count % InnerConst.BATCH_SIZE == 0 ? 0 : 1;
            //分批写入数据
            for (int i = 1; i <= batchNum; i++) {
                // 获取分批数据
                List<List<String>> batchData = getQueryData(req);
                // 写入数据
                excelWriter.write(batchData, writeSheet);
                // 释放内存
                batchData.clear();
            }
​
        } catch (AppPortalException e) {
            e.printStackTrace();
}